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Android Threads and Services But Wait There's More! Messengers and Handlers: Activity

Trainer Workout
Trainer Workout
22,341 Points

How to create an inner Handler class just like we did with GeolocationService.

MainActivity.java
// some methods omitted
public class MainActivity extends Activity {
    Boolean isBound = false;
    Messenger mServiceMessenger;
    Messenger activityMessenger = new Messenger(new ActivityHandler(this));

    ServiceConnection mServiceConnection = new ServiceConnection() {
      @Override  
      public void onServiceConnected(ComponentName name, IBinder binder) {
        isBound = true;
        mServiceMessenger = new Messenger(binder);
      } // onServiceConnected()

      @Override
      public void onServiceDisconnected(ComponentName name) {
        isBound = false;
      }
    };

  private class ActivityHandler extends Handler {
    private MainActivity mainActivity;

    public ActivityHandler(MainActivity mainActivity) {
        this.mainActivity = mainActivity;
    } // ActivityHandler()
  } // ActivityHandler
} // MainActivity
GeolocationService.java
// some methods omitted
public class GeolocationService extends Service {
    int mLatitude;
    int mLongitude;
    Messenger mMessenger = new Messenger(new LocationHandler());

    @Override
    public IBinder onBind(Intent intent) {
      return mMessenger.getBinder();
    }

   class LocationHandler extends Handler {
      @Override
      public void handleMessage(Message msg) {
        mLatitude = getLatitude();
        mLongitude = getLongitude();
      } // handleMessage()
    } // LocationHandler
} // GeolocationService
Difficulty.java
  public class Difficulty {
    public static Boolean HARDMODE = false;    
  }

3 Answers

Seth Kroger
Seth Kroger
56,393 Points

Much like the GeoLocationService challenge, when the Handler is an inner class, you don't need to store a reference to the outer class object. This has to do with the way (non-static) inner classes work in general . Objects of inner classes can't exist outside of an object of the outer class and they automatically have access to the methods and member variables of the outer object. You don't need the reference to the MainActivity yourself because that reference is already embedded.

Trainer Workout
Trainer Workout
22,341 Points

Looks like I'm not learning from my mistakes :-). Thanks again.

I'm attempting this without the reference to MainActivity and receiving the same error three years later.

public class MainActivity extends Activity {
    Boolean isBound = false;
    Messenger mServiceMessenger;
    Messenger mActivityMessenger = new Messenger(new InnerHandler());

    ServiceConnection mServiceConnection = new ServiceConnection() {
      @Override  
      public void onServiceConnected(ComponentName name, IBinder binder) {
        isBound = true;
        mServiceMessenger = new Messenger(binder);
      }

      @Override
      public void onServiceDisconnected(ComponentName name) {
        isBound = false;
      }
    };

    class InnerHandler extends Handler {
      @Override
      public void handleMessage(Message msg) {
        super.handleMessage(msg);
      }

    } 
}

try this: class mActivityHandler extends Handler{ @Override public void handlerMessage(Message msg) } } }

class ActivityHandler extends Handler {

 @Override
  public void handleMessage(Message msg) {

   mServiceMessenger =   new Messenger(new ActivityHandler());

} 

}

and it worked